1. Field of the Invention
The present invention relates to liquid crystal display device and also relates, for example, to a liquid crystal display device of the type employing the so-called lateral electric field scheme.
2. Description of Related Art
The liquid crystal display device of this type is such that a pixel electrode and an opposite or xe2x80x9ccounterxe2x80x9d electrode which are disposed adjacent to each other are formed in a pixel region of a liquid crystal side surface of one substrate of respective substrates being disposed to oppose each other with a layer of liquid crystal material interposed therebetween, wherein components of an electric field created between these respective electrodes which are in parallel to the substrate are used to cause molecules of the liquid crystal material to take behavioral actions.
And, the one that applies this lateral electric field scheme to an active matrix type display device is arranged to use as pixel regions respective regions which are surrounded by a great number of parallel-provided gate signal lines extending on the liquid crystal side surface of one substrate in an xe2x80x9cxxe2x80x9d direction thereof and a great number of parallel-provided drain signal lines extending on the substrate surface in a xe2x80x9cyxe2x80x9d direction thereof and comprise in each of these pixel regions a thin-film transistor which is made active in response to receipt of a scan signal from a gate signal line and the aforesaid pixel electrode to which an image or video signal is supplied from a drain signal line through this thin-film transistor and also the counter electrode to which a signal is supplied which becomes a reference with respect to the image signal.
In addition, in view of the fact that the electric field for permitting liquid crystals to take behavioral actions is inherently weak and faint, the pixel electrode and the counter electrode are formed into band-like shapes respectively, at least one of which consists of a plurality of ones that becomes a comb-tooth like pattern while letting them be disposed alternately.
And, one is known in which the pixel electrode and the counter electrode are formed of different layers with a protective film sandwiched therebetween, wherein the protective film is comprised for example of an organic material layer which covers the thin-film transistor.
Due to this, an orientation film which determines the initial alignment of liquid crystal molecules is to be formed to cover the organic material layer for use as the protective film and one electrode of the above-noted pixel electrode and counter electrode.
However, it has been found that in the liquid crystal display device thus arranged in the way stated above, each of the following phenomena occurs due to unusual matter of the orientation film which is formed in direct contact with the liquid crystals.
More specifically, in cases where vibration shocksxe2x80x94in particular, vibrations at high-frequency wavesxe2x80x94are applied to the liquid crystal display device, unwanted separation or peel-off takes place at the orientation film, causing bright points to generate on the entire surface of a display plane. The result of disassembling for investigation such liquid crystal display device has revealed that peel-off occurs at a portion of the orientation film overlying an electrode in a manner as shown in FIG. 9 (this phenomenon will be referred to as xe2x80x9cMode 1xe2x80x9d hereinafter).
The bright points can also generate when the liquid crystal display device is continuously driven in a vibration-free state. As a result of disassembling for investigation this liquid crystal display device, it has been found that peel-off generates at part of the orientation film overlying the protective film as shown in FIG. 10 (this phenomenon will be referred to hereinafter as xe2x80x9cMode 2xe2x80x9d).
In addition, the bright points can gradually generate even in the so-called temperature cycling test which recurrently changes an ambient temperature of the liquid crystal display device between low and high temperatures. As a result of disassembling for investigation such liquid crystal display device, it has been found that the orientation film overlying an electrode is liberated with respect to this electrode as shown in FIG. 11A (this phenomenon will be referred to hereinafter as xe2x80x9cMode 3xe2x80x9d). Note that FIG. 11B is a cross-sectional diagram as taken along line bxe2x80x94b of FIG. 11A.
Additionally each view of FIGS. 9, 10 and 11A is a drawing which corresponds to FIG. 3 which will be later presented.
The present invention has been made in light of the above-discussed technical background, and one of the advantages of this invention is to provide a liquid crystal display device which comprises an orientation film(s) with increased reliability.
A brief explanation will be given of the summary of representative ones of the inventive concepts as disclosed herein.
(1) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a insulating film and an orientation film is formed at an upper surface of the insulating film in such a way as to cover one of the pair of electrodes, a silane coupling material be mixed into the orientation film at a specific mixture ratio which is equal to or more than 0.1% and yet less than or equal to 2% with respect to an orientation film solid content concentration.
(2) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a insulating film and an orientation film is formed at an upper surface of the insulating film in such a way as to cover one of the pair of electrodes, wherein the orientation film is formed with its temperature suppressed to less than or equal to 250xc2x0 C. during firing or baking in the fabrication thereof.
(3) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a insulating film and an orientation film is formed at an upper surface of the insulating film in such a way as to cover one of the pair of electrodes, that the above-noted one electrode exhibits a zigzag-shaped pattern having a plurality of bent portions along the extending direction thereof, and that the other electrode is disposed in parallel to the above-mentioned electrode.
(4) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a insulating film and an orientation film is formed at an upper surface of the insulating film in such a way as to cover one of the pair of electrodes, and that the orientation film is designed so that its film thickness falls within a range of from 60 to 250 nanometers (nm).
(5) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a insulating film and an orientation film is formed at an upper surface of the insulating film in such a way as to cover one of the pair of electrodes, that an orientation film is formed at an upper surface of the dielectric film in such a way as to cover one electrode of the pair of electrodes also, and that the orientation film is less than or equal to 95% in imidization ratio.
(6) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a protective film and an orientation film is formed at an upper surface of the protective film in such a way as to cover one of the pair of electrodes, that the protective film is comprised of either an organic material layer or a sequential multilayer structure consisting of more than one inorganic material layer and more than one organic material layer, and that the film thickness of the orientation film over the protective film is designed to be greater than the film thickness of the orientation film over the above-stated one electrode.
(7) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a protective film and an orientation film is formed at an upper surface of the protective film in such a way as to cover one of the pair of electrodes, and that the orientation film is arranged so that its film thickness is different in each region as subdivided into a plurality of ones.
(8) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a protective film and an orientation film is formed at an upper surface of the protective film in such a way as to cover one of the pair of electrodes, and that a side-wall surface of the aforesaid one electrode is such that a taper is formed to have a trapezoidal shape when looking at from a bottom surface to upper surface of the one electrode.
(9) A liquid crystal display device in accordance with the present invention is, for example, in that a pair of neighboring electrodes are disposed with a protective film comprised of either an organic material layer or a sequential multilayer structure consisting of an inorganic material layer and an organic material layer interposed between them in each pixel region on the liquid crystal side surface of one substrate, an orientation film is formed at an upper surface of the organic material film in such a way as to cover one electrode of the pair of electrodes, the pair of electrodes are each arranged as an electrode group consisting of a plurality of electrodes, and that respective subdivided regions occupied by the one electrode are four regions or more whereas respective divided regions occupied by exposed part of the organic material layer are three regions or more.
(10) A liquid crystal display device in accordance with the present invention is, for example, the one that is arranged based on the arrangement of any one of the (1) to (9), wherein each pixel region is arranged to be surrounded by a pair of gate signal lines and a pair of drain signal lines and comprises within its region a thin-film transistor as rendered active by a scan signal coming from a gate signal line and a pixel electrode to which an image or video signal is supplied from a drain signal line through this thin-film transistor and also a counter electrode to which a signal for use as a reference with respect to the image signal is supplied, characterized in that the pixel electrode and the counter electrode are used to constitute the above-noted pair of electrodes.
(11) A liquid crystal display device in accordance with the present invention is the one that is arranged based on the arrangement of the (10) by way of example, characterized in that a counter electrode consisting essentially of a plurality of electrode groups is formed above the upper surface of the protective film which is comprised of either an organic material layer being formed to cover the thin-film transistor also or a multilayer structure of inorganic and organic material layers, and characterized by having a counter electrode of these respective counter electrodes whose center axis is made identical to and superposed with the center axis of a drain signal line and which is formed to have a width greater than a width of the drain signal line.
(12) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a protective film comprised of an organic film and is in contact with an orientation film, wherein a film thickness of the orientation film overlying the protective film is greater than a film thickness of the orientation film overlying an electrodes being formed on the protective film.
(13) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a protective film comprised of an organic film and is in contact with an orientation film, wherein said pair of electrodes have a plurality of electrodes respectively, and having plurality of regions formed between the electrodes with difference in film thickness of the orientation film.
(14) A liquid crystal display device in accordance with the present invention is, for example, a pair of substrates with a liquid crystal layer therebetween, a pair of electrodes disposed adjacent to each other in each pixel region of a liquid crystal side surface of one of the pair of substrates, at least one of the pair of electrodes being formed on a protective film comprised of an organic film and is in contact with an orientation film, wherein at least one of said pair of electrodes has a taper shape with a width on said protective film side being narrower than a width on said liquid crystal side.